Our work is aimed at elucidating the nature of the type 1 and type 3 sites of copper-containing proteins. These proteins are found in a diverse variety of organisms and are involved in many important physiological redox processes. The elucidation of these processes must be based upon an intimate understanding of the structure as well as the chemical properties of the copper centers. The experiments proposed to characterize the type 1 site include: (1) 1H nmr studies aimed at identifying ligand groups. (2) Metal replacement studies and physical studies of these derivatives and (3) attempts to synthesize analogues of the type 1 site. Studies proposed for the type 3 site include ligand binding studies and epr studies of the partially reduced type 3 site.